Multiple program traffic control systems



y 12, 1964 G. E. FIESER ETAL 3,133,264

MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS Filed Feb. 26, 1957 4 Sheets-Sheet 1 CENTRAL STATION F I G. l

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Attorney May 12, 1964 G. E. FIESER ETAL MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS 4 Sheets-Sheet 2 Filed Feb. 26, 195'? L mm 055 TE NHH. m 0 E n .6 N w ,0 1 MM c m mm m mm: mm: 51$: mm: mm: mmzmmz MM [l 0 x95: W M15655". A W V: mm m: B m N: F

mm EOPOE 3020x525 No Ow m mm W P ll 9 s s s s 32 29 82 m8. 32 P (QN mm a e e 0 Q R mm H mm 21 v y 12, 1964 s. E. FIESER ETAL 3,133,264

MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS Filed Feb. 26, 1957 4 Sheets-Sheet 3 INVENTORS 9 GARLAND E. F/ESER q' A/VD 00mm n! SCH/PEPE]. 0 (1') Attorney May 12, 1964 G. E. FIESER ETAL 3,133,254

MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS SYNCHRONOUS MOTOR v \/-M I FIG? INVENTORS GARLAND E F/ESER A/YD DONALD l6. SCHREPEL Attorney United States 1 Patent 3,133,264 MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS Garland E. Fieser, East Moline, and Donald W. Schrepel, Molina, 111.; said Fieser assignor, by mesne assignments, to The Gamewell Company, Newton, Mass., a corporation of Delaware Filed Feb. 26, 1957, Ser. No. 642,469 9 Claims. (Cl. 340-49) The invention relates to systems which control the How of traflic across a number of intersections of traflic paths which comprise a central'station and a plurality of coordinated outlying local stations. The traffic paths may be railroad tracks, highways, city streets, or foot paths. Trailic across these intersections is usually controlled by signals of some sort which give the right of way alternately to one and then the other intersecting path.

The invention, though not limited to autos moving on city streets, will be illustrated as applied to city streets on which traiiic flows across successive intersections and is controlled by changing trafiic signals. The signals, usually lights at a given intersection include at least a go signal, a stop signal, and a caution signaL' Usually the go signal is a green light, the stop signal is usually a red light, and the caution signal, indicating that the other signals are about to change, is usually an amber light.

Usually the amber signal follows the green signal, giving notice of an impending change of signals from green, allowing passage, to the red signal, forbidding passage. Sometimes amber also appears after ared signal before the green appears. I

At each intersection apparatus referred to herein as. a Local Station is provided which changes the position of switches at the proper time to cause the signals to appear according to a program.

More specifically the invention relates to such trafiic systems. that are adapted to operate according to one of aconsiderable number of programs. The program to be used is selected from the central station.

traffic flows through an area controlled by the system with the least interruption. l I i It is obvious that in giving the green light to a car on one path, a car on'the intersecting path has to stop for a red light. If we assume that at a given'time twice as many cars go east and west than north and south, "twice as much time might be given for the green on east and west than for north and south.

Usually one street is more important than the ot er: it is customary to refer to one street as the main street and the other as the cross street. The time that is'required to allow traffic to flow first on the cross street, then on the main street, is referred to asa' Cycle. Loolcing down main street at the. time when trafiic on the main street has the-go signal, the cycle will consist of the sum of the time required to display the caution signal, the

stop signal, and then to complete the period during which i the go signal is'displayed. i i

The cycle is divided between two periods; During the a stop, the ideal program will allow as many cars as possible to move at a uniform rate past successive inter- Under each trafiic condition the local stations are so coordinated that a fraction.

I first period green, followed by amber is on the main street.

3,133,264 Patented May 12, 1964 sections so that, looking along one path, one is green, the next red, the next green, so that trafiic may flow at a uniform rate if the distances between streets are all the same length. If there are long and short blocks, it may be desirable to speed up, or to delay, the signal of the one intersection relative to the intersections that are considered typical.

The percentage of a cycle length by which the initiation of a cycle at one intersection is delayed or advanced relative to the initiation of a cycle at other intersections is called the Offset.

It thus appears that if the entire system is properly coordinated the cycle length at all intersections, and the split and the oiiset at each station, must be co-ordinated.

Experience has shown that any assumed preponderance of traffic in one direction will change during various periods of a day. It is obvious that there will be at least three traflic conditionsmorning rush, normal day, and evening rush. Existing systems usually provide a central station that can change the operation of local stations to conform to any one of three programs. Each program represents a particular combination of cycle length, split, ofifset. Each local station has three dials and the selection of all dials No. 1 give one program, dials No. 2 another program, and dials No. 3 a third. It follows that with most existing systems there can be no more than'three programs, and in each program a particular combination of cycle, spilt, and offset are associated. i

The primary object of the invention is to give greater flexibility to a traific control system. It permits the cycle length to be varied by infinitesimal increments. Having selected the cycle length, the central station can select any one of four splits and any one of four ofisets at each local station. 7

Where a traflic control system hassuch flexibility, and as new equipment is added as the city grows, diiliculty may be experienced withback fcedS -the closing of switches at one local station placing current on connecting channels that will actuate other local controllers in a manner not anticipated. I i

' A second object of the invention therefore is to connect the central station to a selector at the local station in a manner that will cause a mechanical device at the station to runat a speed and in a manner determined by the central station. The central station does not transmit any'signals directly to the apparatus that controls the changing light pattern at an intersection. The mechanical device in the selector, using local current, will place current at the proper time on the apparatus controlling each signal light. Since the electrical system leading from the central station to the mechanical device in the selector and the electrical system controlled by the mechanical device that leads to the traffic lights have no common electrical elemenathere can be no feed back.

Another'obiect isto provide local controllers that will used to a caution light at a given intersection having a certain duration. If this light stays on a longer or a shorter timethan the driver anticipates the drivergets confused. Hence, though the cycle length'at a given localsta'tion varies, the time the amber is on should remain unchanged. In the three dial systems described, each of the three dials can be set for the samelength amber-"- but if the cycle length is varied independent of other factors or if there is only-one dial, this fixed len'gthof ambcrislost. I

5 Another object of the invention is-to synchronize the local stations in a manner that, if the linefrom the wntral' station to the' local stations should fail to function, each local station will continue to function as an independent unit.

In most existing systems the signal changes are brought about by the use of local current. To make sure the signals at adjacent intersections remain in step, all the local controllers come to a stop at the end of a cycle and are started off on the next cycle by a synchronizing pulse received from the central station. Should the line connecting the central station with local stations be broken, all local controllers might come to a complete stop at the end of a cycle and traffic over the entire city might be tied up. To avoid this, the invention synchronizes in such a manner that, should the synchronizing current fail, each local coitroller would continue to function as an independent, non-synchronized traflic controller.

Another object is to avoid transitional cycles of abnormal length. The cycle has been defined as the time that elapses from the time caution goes on for traffic in a given path and both the stop and go signal periods are completed. Normally these cycles are of the same length.

However, if the offset is changed during a cycle, that cycle obviously will be longer or shorterthis is called a transitional cycle. In existing systems, if the offset is changed, the local controller is thrown out of synchronism and must Wait until the next synchronizing pulse may come.

To illustrate with an extreme case, the cycle at a given time may be 60 seconds. Let us assume further that there is a split into 20 seconds for the cross street, 4-0 seconds for the main street. If during the change of offset the local controller is brought out of synchronism, it may have to Wait almost 60 seconds-let us assume it waits 50 seconds before it starts. Then, if that offset change came when the cross street had the right of way, we will have a transitional cycle of 110 seconds, divided 20 seconds for main street and 90 seconds for the cross street. Such a transitional cycle will confoundtraffic for quite some time thereafter.

The invention avoids this by dividing the extra time that goes into the transitional cycle over several cycles and always in proportion to the split being used.

The cycle length of a controller, momentarily out of step, is shortened or lengthened depending upon which will require the least time to get into step. The controller does not stop but rather runs on a slower or faster total cycle ratio and maintains the desired split even through this transition period.

Another object is to reduce the time required to change to a difierent offset by either lengthening or shortening the transitional cycle-whichever requires the least time to accomplish.

The invention contemplates selecting, at the central station, the cycle length by changing the speed of a mechanical device at the selector at each local station, and selecting which switches controlled by that device should determine the olfset. To reduce the period of confusion in changing from one pattern of operation to another, the shift of the mechanical device to allow for a different offset should be made. To accomplish this a reversible motor is used to advance or to retard the switches relative to the shaft driven at aconstant speed related to the length of the cycle.

FIGURE 1 indicates, diagrammatically, a system incorporating the invention.

FIGURE 2is a plan view of a portion of the apparatus at each station in FIGURE 1 of the system drawn to a larger scale.

FIGURE 3 is a section taken along line 33 in FIG- URE 2.

FIGURE 4 is a section taken along line 4-4 in FIG- URE 2. FIGURE 5 is a section taken along line 5--5 in FIG- FIGURE 6, shows diagrammatically, the apparatus at the central station indicated at 1 in FIGURE 1.

FIGURE 7 is a wiring diagram.

FIGURE 8 is an exploded view showing a portion of a modified dial.

FIGURE 9 shows a typical relay.

FIGURE 10 shows a modified form of some of the elements of FIGURE 1 when three traflic paths intersect.

The invention will first be described as applied to the usual intersections of two paths--a main street and a cross street.

"1 indicates the central station that controls the local stations both as to the length of the cycle, the split, the offset, and also their synchronization. The term local station includes all of the apparatus at a street intersection that is required to control the change of signals at that intersection.

At each local station there is a selector 2 shown in detail in FIGURE 2. Each selector is connected to the central station by six channels20, 21, 22, 23, 24, 25, not counting the common return. In the illustration the common return is not shown, the various units which are sometimes connected to a common return, being shown grounded.

Only two local selectors are shown in FIGURE 1 though it is understood that there may be a large number of selectors in the system.

Each selector controls a timing device generally indicated at 3 and also shown in part in FIGURE 8. In existing traffic signal systems such timing devices are referred to as dials. The timing device will be so referred to herein. Each dial permits adjustment of the cam shown relative to each other.

The dial controls the operation of a stepping switch 4. The selector and the dial determine when the traffic signals generally indicated at 5 are to be changed by the stepping switch. The traffic signals are here illustrated by three lights 50, 51, 52 which may respectively show amber, green, and red on main street and three lights 53, 54, 55 that show amber, green, and red respectively on the cross street.

.The stepping switch 4 has a shaft 46 carrying eight cams. Cams 40-45 each control one of switches 40s-45s. To facilitate associating each switch with the cam or relay actuating it, the switch carries the cam or relay number which controls it, followed by an s. As shown, the cams have raised portions, and when the follower of the switch is in contact with the raised portion, the switch is closed. Each of these switches connect line '8 supplying current to one of the traffic lights 50-55 at a time determined by the shape and relative position of the raised portions of each of the particular cams 40-45. Cam 49 on shaft 46 controls switch 49s that places at appropriate time current from line 8 on line 76 leading to relay 70. Cam 59 on shaft 46 controls switch 59s used in keeping shaft 36 of dial 3 and shaft 46 in proper relationship.

The shaft 46 is moved by solenoid 48 that actuates ratchet wheel 47 on the shaft. While only six signals 50- 55 are shown, it is obvious that by placing more cams in the stepping switch and more steps on ratchet 47 more signals can be controlled. Thus intersections of more than two streets requiring morethan six traflic lights may be controlled. It is also obvious that the traflic signals can be of any electrically controlled type and are not limited to street lights.

The dial 3 at each intersection does not run continuously but it does make one revolution during each cycle. The

vdial at any other intersection does the same. This dial runs at a fixed speed duringthe time all signal changes that are required to. shift the right of way from one street to the other are made,'then stops until the next shift of right of way is to be made. I

The cycles at the various street intersections "are set to start at fixed, related, intervals to permit the smooth flow of traffic through successive street intersections. Should one dial lose or gain in travel relative to other dials, the flow of traffic would be adversely affected. Hence it is customary to provide for synchronizing the operation of all dials. Channel 21leading from the central station to each local selector is used, in a manner to be described more fully, to synchronize all selectors. Each selector then sends out an impulse at the proper time to its dial.

The function of the dial shown in FIGURE 1 and generally indicated at 3 is to provide current at the proper time to actuate stepping solenoid 43 to move the shaft 46, and the cams carried by the shaft, one stepat a time to change the signals at a particular intersection.

The dial in FIGURE 1 is shown in the position when a cycle is approaching completion, traflic is flowing on main street with a go signal, and when the apparatus is awaiting a signal from selector 2 to terminate the first part of the cycle.

The dial has a shaft 36 that can be driven by a motor 37 at a constant speed sufiiciently fast to make a half revolution in less time than is required to complete the shortest split of the shortest cycle for which the apparatus is designed. The shaft 36 carries cams 36-33 which respectively control switches s33s.

While the dial 3 is shown diagrammatically with a cam 30 having several projections in fixed relation to each other, each of the projections 74, 78, it is shown in exploded view, FIGURE 8 as an arm mounted independently of the other arms on the shaft Each arm carries a set screw 120 that permits setting the arm in a particular relation to the dial disc 121 that is permanently fastened to the shaft 36 such as by a pin 123. In this way the positions of the projections can be varied to secure any desired length of the amber light period. It will be recalled when shaft 36 runs, it runs at a fixed speed and the angular position of the projections 74, 73, 3t? determine When the ratchet 47 is to be actuated.

Motor 37 receives its current over line 38 that connects with switch 70s. In the position shown, with relay 70 deenergized, switch 795 connects with line 71 that leads to switch 33s which is shown as open. Accordingly, the shaft 36 is at rest. When current comes over line 58 from the selector 2 to line' 71, it passes over switch 70s to line 38 andthe motor 37 starts to turn shaft 36 in the.

direction of the arrow. This turns cam 33 and closes switch 33s that now provides current from L2 over lines 79, 7.. over switch 33s and line 71, switch 70s and line 33 to continue running motor 37 after current ceases to flow over 58. The shaft 36 therefore continues to revolve and a projection 011 cam 31 closes switch 31s and current now flows from line 8 line 79, switch 31s, line 73, to ratchet solenoid 48. This will turn shaft 46 one step and the cams carried thereby are'usually set so that the'switch 31s causes cam 40 to close switch 40s to'turn' on the amber signal on main street, while cam 41 opens switch llis and thus turns off the green signal on main street.

As dial shaft 36 continues to revolve, a projection 74 on cam 30 closes switch 30s. This places current on ratchet motor 48 if switch 5% is already closed. Current thenflows from L3 over line 8, switch 59s, line 75, switch 36s to ratchet motor 48 and shaft 46 moves another step. The initial contact is'niade by cam 31, and the next contact by cam 36 if switch 59s is closed primarily to assure that stepping switch shaft 46 is in a particular position when the selector places current on line 58 to start a new cycle.

No matter in what position shaft 46 is whenthe cam 31 closes switch 313 to terminate the first'part of the cycle, solenoid 48 will move shaft 46 one step. If the shaft is in the position shown, that will move cam 59 to a position where cam 59 has closed switch 59s and as cam 36 sends out subsequent inipulsesby closing switch 3th, currentwill ilowover switch 59s as described to switch'3lls and on to ratchet solenoid 48.

However, if shaft 46 is not in the positionshown, the

. 5 ratchetsolenoid 48 will respond to earn 30 and switch 30s only until green is on main street and then cam 59 will open switch 59s. The shaft 46 now stops until the termination of the first part of the cycle starts when cam 31 will close switch 31s and again start shaft 46.

If at the start of a new cycle the shaft 46 is in proper position, cam 41 is holding switch 41s closed giving a green light 51 on main street and cam holds switch 45s closed giving a red light 55 on the cross street. If ratchet solenoid 43 is actuated, the shaft 46 carries the cams to a position where cam 40 closes switch 49s energizing amber light 50 on the main street, cam 41 opens switch 41s turning off main street green signal 51. However cam 45 still holds switch 45s closed, keeping the red signal on the cross street. It will be noted that the length of theamber period is fixed by the relative position of cams 3t) and 31 and the constant speed of motor 3'7. When the shaft '46 has made the second step initiated by projection 74 the projection on cam 49 closes switch 49s and 'places current from line 8 on line. 76 that energizes relay 70 and draws switch 70s into contact with line 77. Current now flows over line 79, switch 32s, line 77, switch 70s, line 38 to, keep motor 37 running. However when the shaft 36 has'made half a turn cam 32 will open switch 32s whose follower is now in the cam notch and prevents any further flow of power over line 77 which will cut the current off line 38 and stop the motor of switch 32s out of the notch in-cam 32. and current now flows from L2 over line 79, switch 32s and line 77 to motor 37 and keeps it running even though the current over line 57 ceases.

Projcction78 on cam 30 will now closecontact 30s and cause ratchet solenoid 48 to step shaft 46 one step if cam 59 holds switch 595 closed. That will place amber on the cross street, turn off the green on the cross street, leavered on the main street. p

After the lapse of time desired for the fixed amber period, projection 86 on cam 30 again closes switch 36s and this causes the shaft 46 to be moved one more step. This will place the green on the main street and the red on the cross street. The shaft 36 now continues to run at a fixed speed until-cam 33 again opens switch '33s. This stops rnotor 37. Thus, the single dial ,3 will, each time it is started by current on either line 57, or 53, turn through a half turn and in so doingwill turn off the green on whichever street itis, turn on the amber onthatstreet for a fixed time, then turn on the redlight, while on the other street the red is held while the amber is on the first named street,then changes to green.

When this change from green to red and red to'green on the two streets is accomplished, the dial stops and awaits another signal from the selector. In describing the "operation of dial 3 and stepping switch 4 it was noted that current must periodically come from the selector 2 over lines 57 or 58 if the apparatus is to continue in operation. j j I Summarizing, the function of dial 3 is to provide amber signals of fixed length before the green changes to red reg'ardlessof the length of the cycle or the split or offset. The operation of the selector shown in FIGURE 2 Q willnow he explained. Referring to FIGURE 2, and assuming that motor 114 is not energized but motor is energized, it will be clear that motor 66 isenergized, it will be clear that motor 6t) will turn shaft 62 through a gear system. The shaftcarries two, cams 6 3, 64. 1 As will be explained later, motor 60 is normallysupplied with current from the central station overchannel '20 in FIGURE"? and the frequency of that current deter-m mines the speed of motor 60 and thus the length of time it takes for one cycle which is equal to one revolution of shaft 62. The function of these cams 63, 64 is to synchronize this selector 2 with all other selectors by assuring that at one point in the revolution of shaft 62 it will be in a preset relationship to the shaft 62 of all other selectors 2 in the system. Referring to FIGURE 3 it will be seen that each cam is circular but has a step that permits the spring arms 65, 66. to dip at the appropriate time. The contact 67 is open during almost the entire revolution, all except for the short period measured by angle 68. This angle is usually made 1% of one revolution of shaft 62.

Referring to FIGURE 7, it will be seen that during normal operation of the system, with current on channel 20, current will pass through fail-safe relay coil 26 which will draw switch 26s into contact with line 61. This provides current from channel 20 over switch 27s, line 61, switch 26s, line 69, motor 60. During one percent of each revolution of shaft 62, contact 67 is closed and channel 21 is connected over contact 67 to relay coil 27 during that 1% of the revolution of shaft 62. Channel 21 carries a synchronizing current 98% of the time.

If the shaft 62 and cam 96 are in synchronism with the central station, the switch 67 will close during the 2% of the time there is no current on channel 21. Relay coil 27 will not be actuated and switch 27s will not open.

However if shaft 62 gets out of synchronism and closes contact 67 while synchronizing current is on channel 21 the relay 27 will attract armature 27s and break the circuit to the motor 60 which will now stop until the current flow in channel 21 again ceases at the end of the cycle. That allows relay 27 to permit armature 27s to reestablish current flow to motor 60. Thus the shaft 62 is synchronized with similar shafts in all selectors in the system.

One of the features of the circuit is that if for some reason variable frequency channel 20 fails to function, relay 26 which is normally held closed will open, armature 26s will make contact between line 28 and motor 60. The motor 60 will then cause the selector to function independent of the central station and traffic signal will be changed even though on a program not co-ordinated with adjacent intersections.

The manner in which motor 60 actuates apparatus to place current on lines 57 and 58 to initiate each split of the cycle will now be described. 91 indicates the carrier gear of a differential transmission, riding free on shaft 62 and rotatably supporting double gears each having toothed portions 9394 meshed respectively with pinion 92 and gear 95. While gear 91 is held at rest by a gear 115, pinion 92 which is permanently fixed to shaft 62 through double gears 9394 will tum pinion 95 riding free on shaft 62. Through interposed gearing this pinion 95 drives shaft 96 carrying at least four pairs of cams 100, 101, 102, 103 for controlling contacts 100s, 101s, 102s and 103s (see FIGS. 2 and 7). With gear 91 at rest, the speeds of shaft 62 and 96 are the same if the various gears between shafts 62 and 96 are properly selected. I

The drawing shows three addition pairs of cams 104, 105, 106 that may be used in the modified form of the invention to be described later.

.The purpose of cams 101, 102, 103 is to close contacts which provide current on line 58 at a time depending on the cycle desired, to initiate movement of dial 3 to terminate the first part of the cycle as, previously defined.

The purpose of cams 100 is to close a contact 100s that places current on line 57 at the proper time to initiate movement of dial 3 to terminate the second part of URES 2 and 4 show cams 100A, 100B, forming cam pair 100. Each cam can be adjusted by set screws 97 to any desired angular position on shaft 96. The cams of any pair are usually adjusted relative to each other so that angle 68B is about 18 degrees. Each cam has a drop and a spring contact arm or 66, that close a contact between its arm 65, 66.

Each of the cam pairs 101, 102, 103 is set on shaft '96 at a different angular position relative to earn 100 and any one of the three cams can close a contact to place current on line 58 to initiate termination of the first portion of the cycle. Thus cams 101 may be set to close contact 101s a half revolution before cam 100 closes contact 100s, that would be a 50-60 split. Cam 102 may be set to close its contact 102s /3 of a revolution before cam 100 closes contact 100s, that will give a 33- 67% split of whatever total cycle length is selected.

Each of these contacts 101s, 102s, 103s can supply power, if currentis supplied to the line containing the contact, to line 58 which feeds current over switch s in the position shown in FIGURE 7 to line 38 leading to motor 37 to keep it in operation through the termination of the first portion of the cycle. Which of cam pairs 101, 102, 103 is to determine the split is decided by the central station which controls relays that supply current to one of the contacts controlled by the cam pairs. Channel 25 leads to relay coil 11 which controls the position of two switches 11s. The relays in the selector controlled by lines 20 to 25 are generally similar, some, like relay 11 illustrated in FIGURE 9 control two switches, others only one switch. Referring to FIGURE 9, channel 25 leads to a grounded relay coil 11. The frame 124 which carries relay coil 11 also carries the screw 125. Separated by insulated discs are a number of elements including two flexible arms forming switches 11s. The frame 124 pivotally supports armature 126 that moves pillar 127. Pillar 127 moves switches 11s from their normal position. If current is on channel 25, current which otherwise goes to line 83 will be switched to line 85.

If neither channels 24 or 25 carry current from the central station to the selectors, the switches 10s and 11s will be in the position shown in FIGURE 7 and current flows from L2 over line 81, switch 10s, line 82, switch 11s to line 83-and thence line 58 at the instant when contact 103s is closed. This contact is closed by cam 103, as described, only for a short time during the revolution of shaft 96. At that instant, current flows over line 58 toswitch 70s.

If current is placed on channel 25 at the central station,

switches 11s are moved, and now, to start the termination of the first portion of the cycle current must flow over line 81, switch 10s, line' 82, switch 11s, line 85, contact 102s, line 58, switch 70s, line 38 to motor 37. This differs from the previously described circuit only in that contact 102s is substituted for contact 103s. Therefore, cams 102 now determine the split and not cams 103. If current at the central station is placed on channel 24, relay coil 10 will be energized and move switch 10s. To start the termination of the first portion of the cycle current must now flow over- 81, switch 10s, line 86, switch 101s, line 58, switch 70s, line 38. This will happen when cam 101, on shaft 96 in FIGURE 2 close contacts 101s.

It has been shown that the selector has a normal split, governed by cams 103, but that by placing current at the central station on the proper channels, the split created by each selector will be determined by cams 101 or 102. All three sets of cams 101, 102, 103 can be set on shaft 96 so that each cam pair gives any desired split. Thus the selector will initiate the termination of the first portion of each cycle by placing current on line 58 at a time determined by whether channel 24, or channel 25, or neither is energized.

-As described, the current on line 58 initiates the opera tion of motor 37 and that causes the gdsignal on main street to be terminated, the caution signal to be held for a fixed time, and then the stop signal to be shown on main street while a go signal appears on the cross street. Motor 37, after turning shaft 36 through a set part of a revolution, stops. j

, Meanwhile shaft 96 continues to turn and in due, course the cams 100 place current on line 57. i

This contact on the arms controlled by cams 100 is shown at 100s in FIGURE 7. This contact allows current from L2 to flow over line 110, line 111, contact 100s, line 57, switch 70s to line 38 and then to motor 37. Switch 70s was moved from the position shown in FIG- URE 7 at the end of the first portion of the, cycle. If the apparatus is in step, cam 32 will be advanced a half turn from the position shown in FIGURE 1. The short periodduring which contact liltls is closed is sufiicient to allow motor 37 to turn shaft 36 far enough to move cam 32 into position to close switch 32s. Current from L2 will now flow from L2 over line '79, switch 32s, line '77, switch 76s and line 38 to motor 37 continuing the motor in operation. As already described, the dial 3 will now actuate the stepping switch 4 as needed and change the lights 50-55 to transfer the flow of traffic from the cross street back to the main street. When the shaft 46 in stepping switch 4 has turned far enough to turn on the amber, then the red, cam 49 closes a circuit over line 76 that places current on relay coil 70 which moves switch 7th to break the circuit that has kept the motor 37 running. As previously explained, switch 70s is not connected with line 57 until termination of the first portion of the cycle which shifts traffic from the main street to the cross street has been completed. Then, with relay 70 energized and the'switch '70s moved into contact with line 77 the closing vof switch liltls determines when the split is to come and places current on line 38 that starts the dial motor 37 to complete the second part of the cycle.

The offsets at a particular intersection are changed by placing current on motor 114 in the selector 2.

The selector is so designed that if the central station calls for a particular offset by placing current on one of the channels leading to the local station, that current will only reach motor 114 if the oifset at which the selector is operating is other than that desired. As soon as the selector operates at the offset desired by the central station, the current is automatically taken off motor 114. Moreover to reduce the time required for this adjustment, control means are provided whereby motor 114 will turn in whichever direction requires the least revolutions of motor 114.,

The motor 114, through gearing, drives a shaft 93 which carries gear 115 and also four sets 116, 11 7, 118, 119 of paired cams 87-458 connected to each other by studs 109. Each pair of cams can be adjusted relative to other pairs angularly, as desired on shaft 98. Each cam 87, see FIGURE 5, has a raised 130111011168 extending over half a circumference for actuation of a corresponding single-pole double-throw motor direction control switch 116R, 117R, 118R,,and 119R. Cam 88, shownbehind cam engages the follower and to line 129 in-FIGURE '7 if the hump on the cam does not engage the follower. The motor 114 is of a type that will turn in one direction when current is placed on line 128 and in the=reverse direction when placed on line 129.

The shaft 98 carries a gear that engages the carrier gear 91. Thus, when motor 114 is supplied with energy, the shaft 96 is advanced or retarded relative to shaft 62 and thus the offset is changed. Current is now placed on line 57 by cam 100, not when contact 67 closes, but at a fixed angular ofiset therefrom.

At any one time current is in only one of the circuits containing switches 116s119s. If there is no current in channel 23 or channel 22, then cam pair 119 determines the ,ofiset.

Referring to FIGURE 7, with switches 13s and 12s in the deenergized position shown, it will be seen that if switch 119s is closed current will flow over switch 119R.

This will place current on either line 128 or line 129, depending on the position of switch 119R, and start motor 114. 'When the motor has turned cam pair 119 to the position shown in FIGURE 5 where the follower falls into notch 107 the switch 119s will open and the motor 114 stops.

As the motor 60 turns through cycle after cycle, the motor 114 stays at rest and the gear 115 holds the carrier gear 91 at rest in the position shown.

If the central station wants the offset to be determined by cam pair 118 rather than by cam pair 119, current is placed on channel 23 to energize coil 12 to move switches 12s. Current now flows from line 110, over switches 13s, 12s to switch 118s. When switch 118s is closed current flows to motor 114. Since cam pair 118 is angularly displaced from cam pair 119, switch 118s will be closed and current will flow to motor 114 to move shaft 98 and gear 115 to the position that gives the offset that corresponds to cam 118. I

If the central station wants the offset to be determined by cam 117 current is placed on channel 22. This actuates relay coil 13 that moves switch 13s and current now flows from line 110, overswitches 13s and 12s to switch 117.9. In the manner described, this will cause motor 114 to turn shaft 98 until the gear 115 has turned gear 91 to a positioncorresponding toa new offset.

If the central station wants the offset to be determined by cam 116, current is placed on both channels 22 and 23. Current now flows from line 110, over switch 13s, switch 12s to switch 116s and if that is closed, over switch 116R to either lines 128 or 129.

It will be noted that changes of offset are accomplished by motor 114 entirely apart from synchronization which is controlled by cams 65, 66 and motor 60.

Therefore, if when the motor 61) is being synchronized a change in offset is in progress, the actuation of motor 114 will merely cause the differential gear 91 to be moved in a manner to change the time when the cycle beginning and split is initiated by cams mil-1&3 carried by shaft 96. At the end of any cycle this change in length of the transitional cycle will be; determinedby the amount of travel of 'shaft 98 necessary to change the offset that is being completed.

The apparatus at each location that directs the flow of trafiic, comprising traffic signals, stepping switch, dial and selector have been described. The central station 1, shown in outline in FIGURE 6, will now be described.

A variable" frequency generator 15 is supplied with cur- I rentfromlines L2 and L1. The frequency transmitted to lines 16 and 17 may be changed by movinglever 18. Line 17 is connected to the, outgoing channel 20 that leads to all local controllers at street intersections. Lines 16 and 17 lead to a variablespeed motor drive 19 that turns the cam 29 to make one revolution for every cycle.

of traffic signal change. I I

Current from L2 flows over switch 29s to channel 21 except when the notchon cam 29 briefly opens the'switch 29s. That interruption of current onchannel 21 is used to synchronize all the selectors in the system in the manner previously described' 9 l i I j i i L2 also supplies current to switches 22s, 23s, 24s, 25s. Closing of either switch 22s or 23s, or both, changes the l1 offset at the selectors by sending current over channels 22 and 23.

Closing of switches 24s or 25s places current on channels 24 or 25 that determine the split at each selector. While these switches 22s-25s are shown as hand actuated, it will be understood that they might be actuated by a programming device of any sort.

The operation of the system will now be described.

A series of plans for handling traffic flow under various conditions such as morning rush, normal traffic, evening rush are first made. A decision is made how long the amber is to stay on and the cams 30, 31 on the dial 3 are set so that one cam 31 will startthe amber interval on the main street, the next cam 74 will start the green interval on the cross street and the red interval on the main street with a set lapse of time. The dial 3 runs always at a fixed rate and comes to a stopafter the green has been shifted from one street to the other. The length of time the amber is on may be set differently for different intersections if desired.

The length of the cycle desired at any particular timethe same throughout the system-is now determined by moving lever 18 to change the frequency of the current sent out over channel 20 from the central station. This determines how fast motor 60 will turn shafts 62 and 96 and the cams 63, 64 and 100-104 carried by these shafts.

When cams 63 and 64 close contact 67, should shaft 62 be out of synchronism, the synchronizing current flowing through channel 21 will open 27s, stopping motor 60 until the central station synchronizing switch 29s opens, allowing 27s to close again starting motor 60 and shaft 62 in stepwith the cam 29 and the shafts at other selectors. Depending on whether current is placed on channel 24, channel 25, or neither, the switch controlled by one of the cams 101-103 is activated. Each of these cams can be set to divide the cycle into different proportions for each street intersection and whenever that cam closes a circuit, the dial is started to display amber for a fixed time on one street and then green on the other street until the dial reaches the stop and until the dial is again released by the cam 100. Thus all the local controllers are synchronized, but they may operate at different splits of a cycle, a cycle that can be varied in length, but is common to all.

When current is placed on channel 22 or channel 23 or both, current is placed on lines controlled by cams 116 to 119. If the local selector is already operating at the offset desired, that switch controlled by the cam will be inthe position shown in FIGURE 5 and no current will pass to motor 114.

If the offset called for is different than the one in use, the switch will transmit current to motor 114 which will turn the planetary system through gear 115, and this will move all thecams in shaft 96 forward or backward to secure the new offset desired.

When these adjustments have been made, the selector will-place current on lines 57, 58 at the-proper times. Each time current is placed on one of these lines the dial 3 is started up to place current at the proper times on ratchet solenoid 48. This steps shaft 46 along so that the traffic flow on the two intersecting streets will be according to the selected cycle, split and offset.

It will be seen that, in contrast to the usual traflic control systems in which the local controllers containa plurality of dials, any one of which can be connected-to circuits coming from a central station whereby current from the central station actuates relays in the-local controller, the actuation of the traffic lights 50 to 55 is controlled entirely by a mechanical deviceshaft 96 and the cams 100-103 carried thereon and shaft 98 and the cams 116-119 carried thereon in FIGURE 2-located at the local intersection. The invention provides means whereby the central station 1 can control the cycle length,

the split, and the offset by sending out current to select .70s for the last split of the cycle.

12 which of the cam pairs -103 shall function and moving the shaft 96 relative to shaft 62 by placing current on motor 114 to change the offset.

As thus far described, the invention applies to the usual traflic intersection consisting of a main and a cross street. However, the invention is not limited thereto. By way of example, for a main street and two cross streets, FIG. 10 shows a stepping switch which may be used in conjunction with the device of FIG. 2 and circuitry of FIG. 7 which are shown as including contacts 104s, 105s, and 106s operated by three cam pairs 104, 105, 106 not utilized in the usual intersection of two traffic lanes. Cams 101, 102, 103 give a choice, as described, of splits between the main and one cross street, whether there are three or only two streets. If there are three streets, one of the three cams 101-103 initiates the termination of the first portion of the cycle and determines when the portion of the cycle to be applied to passage of traffic on the main street will be terminated. One of the cams 104-106 then determines how the remaining part of the cycle is to be split by terminating flow on the first cross street.

It will be noted in FIG. 10, that cams -133 on shaft 136 correspond to cams 30-33 on shaft 36 in FIG. 1. As shown in FIGURE 7, during each cycle the closure of one of switches 101s, 102s, 103s feeds current over line 58, switch 70s to start motor 37. Cam 133 will close switch 33s and provide current over line 71 to keep motor 37 running for a third of a revolution. Then the second of the two notches in cam 133 will stop the motor.

When shaft 96 has turned far enough so that one of cams 104-106 closes a switch 104s-106s that is on a line supplied with current by the prevailing split selection, current will again flow over line 58, switch 70s to start the motor 37. This carries the first cross street through amber to red and places the go signal on the second cross street. 1

Shaft 136 continues to revolve until cam 149, corresponding to cam 49, closes switch 49s placing current on line 76 that actuates relay 70 and moves switch 70s out of contact with line 71 and into contact with line 77. As described, motor 37 will continue until the notch in cam 132 opens switch 32s.

As the shaft 96 continues to revolve cam 100 will close switch 100s and placecurrent on line 57 that Will again start motor 37. This will terminate the third portion of the cycle and permits traflic to flow on the main street.

Thus, during one cycle, referring to FIGURE 1, current is supplied once in each cycle to line 57 and twice to line 58. FIGURE 10 shows modified shafts 136 and 146 that are substituted for shafts 36 and 46 and a six step ratchet 147 substituted for ratchet 47 in FIGURE '1.

Cam 159 functions as cam 59 in FIGURE 1 to keep shaft 146 and shaft 136 in step. Cam 149 determines when the relay 70 is to be energized to prepare switch Cams 140, 141, 142, corresponding to cams 40, 41, 42 previously described, control signals 50, 51, 52 that provide signals controlling flow of traffic on the main street: cams 143, 144, 145, control switches 43s, 44s, 45s and signals 53, 54, 55 on the firstcross street. Cams 163, 164, are duplicates of cams 143, 144,145, but are set at a different angle on shaft 146. They close switches 163s,164s, 165s to control signals 153, 154, 155. These signals, on the second cross street, function as signals 53, 54, 55 on the first cross street.

While the invention has been illustrated as applied to the usual street pattern with traffic lights controlling the flow of cars, with signals consisting of green, amber and red, it will be understood by those familiar with the art that other types of traffic, other kinds of signals, other sequences of signals in a given path could readily be provided by the invention.

We'claim: I i 1. A traffic control system permitting adjustment of 13 trafiic signal operation at various intersections to adapt the signal changes to the flow of traffic, comprising, traffic signals permitting a right-of-way interval and a caution interval first to one street then to an intersecting street, a plurality of local traific controllers each containing a step switch to energize said traffic signals through said intervals, timing means electrically connected to said step switch to energize and time said step switch through a right-of-way interval and a timed caution interval to one street and then stop, a normally continuously driven synchronous motor drivingly connected to "a timing device to normally continuously drive said device, said timing device including a shaft carrying cams which close contacts to energize said timing means at the beginning of each cycle and again at a desired split of said cycle, a differential gear system between said synchronous motor and said shaft, 3 second motor connected to said differential to intermittently drive a normally stationary portion of said differential to rotationally offset said shaft from said synchronous motor, a plurality of offset motor switches, a first plurality of ofiset motor switch operating cams drivingly connected to said second motor and presettable for the degree offset desired, a master controller,

means in said master controller to determine the proper offset to select, offset selector switch means for applying power selectively to said offset motor switches, and electric channels connecting said means in said master controller to said offset selector switch means in said local controllers.

2, A'traffic control system as in claim 1, including a variable frequency generator forming a part of said master controller, the output frequency of said generator substantially inversely proportional to cycle duration, one other electric channel connecting said generator and said synchronous motor driven timing device in each local controller, the speed of saidsynchronous motor thereby made equal to the speed established by said master controller, and the cycle length at each local controller thereby made equal to the cycle length established by said master controller.

3. A trafi'ic controlsystem as claimed in claim 1, in cluding in each said local controller a synchronizing cam located between said synchronous motor and said differential gear system, a synchronizing switch located in operative relationship with said synchronizing cam and closed by said cam at a zero reference point in each cycle of traffic signals and for a short interval thereafter, a relay having a coil connected in circuit with said synchronizing switch andhaving normally closed contacts in circuit with and controlling power to said synchronous motor, first and second additional electric channels connecting said master controller with each said local controllensaid first additional channel being a synchronizing channel and in circuit with said synchronizing switch and said synchronizing relay coil, said secondadditional. channel .being in circuit with said relay contacts and said synchronous motor, zero reference means in said master controller comprising a synchronous motor operated cam and contact means in circuit with said first additional channel, said contact means being closed during the major portion of each cycle of traffic signals and open at azero point in said cycle and for a short time therebeforeand thereafter, a source of power feeding said first additional channel through said contact means, a common source of power. for all said synchronous motors, said common quency generator in said master controller and including 'said second additional channel connecting said generator with said synchronous motor in each said local controller in circuit with said normally closed contacts, said local synchronous motor being de energized when the zero reference point in a local controller is outof step with said zero reference point established by said master controller, and said variable frequency and thereby the length of said traffic signal cycle. being constant for an-interval representative of substantially constant density of trafiic. 4. In a tratlic control system as claimed in claim 1, wherein said second motor is provided with forward and reverse field windings, a second pluralitytof offset switch operating cams drivingly connected to said second motor, each of said second plurality of cams being associated with one of said first plurality of offset switch operating cams and similarly presettable therewith, said second plurality of offset switch operating cams having half of their periphery low and the other half high, a plurality oftwoposition switches each in operative relationship with one of said second plurality of offset switch operating cams and having a movable contact connected to one of said offset motor switches, two fixed contacts in each said twoposition switch connected respectively to said forward field winding and said reverse field Winding to effect said rotational offset in the shortest direction and in the shortest possible time and with least interference to traffic progression.

5. A traific control system permitting adjustment of traflic signal operation at a group of intersections dependent on the flow of traffic, comprising, traffic signals at each intersection for indicating an adjustable right-ofway interval followed by a constant caution interval first for a main street and then for an intersecting street, a plurality of local trafiic controllers each containing a rulti-positio'n switch connected to at least the traflic sig nals at oneintersection to energize said traflic signals during said intervals, a first timing device at each local traffic controller connected to the multi-position switch at said controller to energize said switchduring a rightof-way interval and a caution'interval to one street and then stop and then to the other street and stop, synchronous drive means drivingly connected to a second timing device to energize the first timing device at the beginning of each cycle and again at a desired split of said cycle,

means, offset selector means including a plurality of oifset selector switches and a like plurality of offset switch operating cams drivingly connected to said second drive I means, each of said cams presettable to stop the second drive means for a desired offset, a master controller, offsetjselector means in said master controller to determine the offset, and electric channel means coupling sa1d offset selector means in said master controller to said source of power comprising an adjustable variable freoffset selector means in said local controllers for rendering effective one of said offset selector switches.

6. A traffic control system as claimed in claim 5, including a variable frequency generator forming a part of said master controller, one other electric channel coupling said generator to said synchronous drive means in eachlocal controller, the speed of said synchronous drive means being determined by the'frequency generated at said master controller to establish the cycle length at each short interval thereafter, a relay having a coil connected in circuit with said switch means and having normally closed contacts in circuit with said synchronous drive means, first and second electric channel means connecting saidmaster controller with each said localcontroller,

said first channel means being in circuit with said switch means and said relay coil, said second channel means being in circuit with said relay contacts and said synchronous drive means, zero reference means in said master controller comprising asynchronously driven cam and contact means in circuit with said first channel means, said contact means being closed during the major portion of each cycle of traffic signals and open at a zero point in said cycle, and a common source of power connected to said synchronous drive means, said common source of power comprising an adjustable variable frequency generator in said master controller and including said second channel means connecting said generator with said synchronous drive means in each said local controller in circuit with said normally closed contacts, said local synchronous drive means being de-energized should the zero reference point in a local controller be out of step with said zero reference point established by said master controller.

8. A trafiic signal controller including in combination, an intersection of main and cross streets, trailic signals at said intersection, said signals including at least green, amber, and red signals to each of said streets, at step switch connected to said signals to energize said signals through a complete traific cycle, an amber timing dial connected to said step switch to energize said step switch and to time said amber signal, a split timing means, a plurality of contacts each operatively associated with said split timing means to start said amber timing dial through a first half cycle of revolution, a plurality of other contacts operatively associated with said split timing means selectively connecting an external source to said amber timing dial to start said dial through a second half cycle of revolution, a differential operatively connected to said split timing means, first and second motors operatively connected through said differential to drive said split timing means, said first motor electrically connected to and energized by a remote variable frequency source, a resynchronizing cam connected to and driven by said first motor and maintained in constant reference with an incoming reference signal, said second motor connected across a power source via one of a plurality of offset selector switches and one of the plurality of two position switches, a plurality of ofiset selector cams operatively associated with said olfset selector switches and carried by and driven simultaneously at the same speed and direction by said second motor, a plurality of two-position switch cams operatively associated with said two-position switches and each connected to one of said offset selector cams, said two-position switches connected through said offset selector switches to energize said second motor in a forward or reverse direction dependent on cam position to rotationally displace said split timestablished by said resynchronizing cam, a plurality of offset control circuits for rendering only one of said offset selector cams and switches electrically elfective at a time, and a synchronizing circuit comprised of a cam operated switch on said step switch and first and second contact pairs operatively associated with said amber dial, one of said contacts of said first contact pair connected to a power source through said cam operated switch in a portion of said signal cycle, one of said contacts of said second pair continuously connected to a power source, a plurality of first projections and a single second projectionon said amber dial, said first projections serving to close said first contact pair to step said switch device through all intervals except one, said second projection serving to close said second contact pair to step said step switch device through the one excepted interval.

9. A traific control system as in claim 5, a binary relay combination including a first relay having a movable element connected to a source of power and having first and second output contacts, a second relay having first and second movable elements connected to said first and second output contacts on said first relay, said second relay having first, second, third, and fourth contacts each connected individually to said oifset selector switches, said first and second movable elements on said second relay movable between said first and second contacts and said third and fourth contacts, respectively, said first and second relays having operating coils connected to said electric channel means from said master controller whereby only one of said offset selector switches is connected to said source of power at a time.

References Cited in the file of this patent UNITED STATES PATENTS 2,133,157 Turner et al Oct. 11, 1938 2,194,310 Leanard Mar. 19, 1940 2,249,217 Lomax July 15, 1941 2,279,896 Wilcox Apr. 14, 1942 2,324,051 Alles July 13, 1943 2,451,457 Shepherd Oct. 12, 1948 2,459,429 Jefiers Jan. 18, 1949 2,542,978 Barker Feb. 27, 1951 2,657,375 Paul Oct. 27, 1953 2,702,896 Alles Feb. 22, 1955 2,761,119 Barker et al Aug. 28, 1956 OTHER REFERENCES Traific Control and Facilitation, Ross C. Harger, the American City, September 1948, pp. 143 and 145. 

1. A TRAFFIC CONTROL SYSTEM PERMITTING ADJUSTMENT OF TRAFFIC SIGNAL OPERATION AT VARIOUS INTERSECTIONS TO ADAPT THE SIGNAL CHANGES TO THE FLOW OF TRAFFIC, COMPRISING, TRAFFIC SIGNALS PERMITTING A RIGHT-OF-WAY INTERVAL AND A CAUTION INTERVAL FIRST TO ONE STREET THEM TO AN INTERSECTING STREET, A PLURALITY OF LOCAL TRAFFIC CONTROLLERS EACH CONTAINING A STEP SWITCH TO ENERGIZE SAID TRAFFIC SIGNALS THROUGH SAID INTERVALS, TIMING MEANS ELECTRICALLY CONNECTED TO SAID STEP SWITCH TO ENERGIZE AND TIME SAID STEP SWITCH THROUGH A RIGHT-OF-WAY INTERVAL AND A TIMED CAUTION INTERVAL TO ONE STREET AND THEN STOP, A NORMALLY CONTINUOUSLY DRIVEN SYNCHRONOUS MOTOR DRIVINGLY CONNECTED TO A TIMING DEVICE TO NORMALLY CONTINUOUSLY DRIVE SAID DEVICE, SAID TIMING DEVICE INCLUDING A SHAFT CARRYING CAMS WHICH CLOSE CONTACTS TO ENERGIZE SAID TIMING MEANS AT THE BEGINING OF EACH CYCLE AND AGAIN AT A DESIRED SPLIT OF SAID CYCLE A DIFFERENTIAL GEAR SYSTEM BETWEEN SAID SYNCHRONOUS MOTOR AND SAID SHAFT, A SECOND MOTOR CONNECTED TO SAID DIFFERENTIAL TO INTERMITTENTLY DRIVE NORMALLY STATIONARY PORTION OF SAID DIFFERENTIAL TO ROTATIONALLY OFFSET SAID SHAFT FROM SAID SYNCHRONOUS MOTOR, A PLURALITY OF OFFSET MOTOR SWITCHES, A FIRST PLURALITY OF OFFSET MOTOR SWITCH OPERATING CAMS DRIVINGLY CONNECTED TO SAID SECOND MOTOR AND PRESETTABLE FOR THE DEGREE OFFSET DESIRED, A MASTER CONTROLLER, MEANS IN SAID MASTER CONTROLLER TO DETERMINE THE PROPER OFFSET TO SELECT, OFFSET SELECTOR SWITCH MEANS FOR APPLYING POWER SELECTIVELY TO SAID OFFSET MOTOR SWITCHES, AND ELECTRIC CHANNELS CONNECTING SAID MEANS IN SAID MASTER CONTROLLER TO SAID OFFSET SELECTOR SWITCH MEANS IN SAID LOCAL CONTROLLERS. 